Method and apparatus for connecting cords/filaments

ABSTRACT

An apparatus for welding monofilaments at a loom makes possible a method for a continuous process for weaving monofilaments into fabric. The apparatus comprises a stand ( 15 ) on which is mounted welding apparatus ( 16 ) and a filament alignment block ( 20 ). In the method, a monofilament ( 30   a ) in the loom is welded to the leading end of a monofilament ( 30 ) on a new spool of monofilament. By welding new monofilament to monofilament in the loom, restringing of the loom is avoided.

TECHNICAL FIELD

The invention relates to a method for, and apparatus used to weldthermoplastic materials in a continuous industrial process.

BACKGROUND ART

Looms used in fabric weaving processes are complex and have a number ofcreels, spools, spindles, reeds, drop wire slots, and tensioningfestoons over which each individual filament or cord needs to be strung.This is a time consuming process for one cord, and since a typical boltof fabric may have 600 to 2000 cords, more or less, stringing a loom forinitial operation is a time consuming and difficult process.

Since filaments or cords are ordinarily supplied on a spool or a packagewhich contains a limited supply of cord or filament, if some means werenot provided to keep the loom strung, this process would have to berepeated each time a spool of filament or cord was depleted duringweaving. Fortunately, in industrial looms, some efficiency is recapturedby tying a new spool of cord or filament to the end of a depleted spoolof filament or cord before the depleted end of the cord or filamentpasses through the loom.

In recent years, monofilament materials, such as those described in U.S.Pat. No. 5,173,136 to Agarwal et al., and U.S. Pat. No. 5,743,975 toSinopoli et al., have been gaining acceptance as a reinforcementmaterial in composites. It has been found, however, that conventionalcord tying or splicing does not work for monofilaments sincemonofilaments tend to be stiff and slippery. Knots are too bulky, snagon the equipment, and tend to slip. Also, monofilaments tend to slip outof conventional wrap splices.

In the weaving of monofilaments, especially heavy gauge nylonmonofilaments, it is important to be able to attach one end of afilament to the end of another filament to 1) tie in successive creelsor 2) repair a broken filament broken during weaving.

When it was found that conventional tying and splicing did not work formonofilaments, the inventors tested and collected data on a number ofmethods which might be used in place of tying or splicing and eventuallydecided to try to melt or fuse the individual monofilaments to eachother at the loom. Once it was determined that specific monofilamentmaterials can be fused by welding, the object of the invention was todevelop a method and apparatus to provide an economical process forattaching the cords.

Although it is believed that other welding techniques will work, it wasdecided to use ultrasonic welding in the method.

Ultrasonic welding comprises the generation of high frequency (20 kHz or40 kHz) mechanical vibrations which are transmitted to a welding horn.An ultrasonic welding horn applies a force at the surface of thematerials to be bonded, and uses intermolecular friction at theinterface to melt the material. A force is maintained against thematerial by the welding horn after the vibration is stopped, and uponcooling, a weld is produced.

Strother, in U.S. Pat. No. 3,184,363 describes an apparatus for splicingthermoplastic cords which comprise an apparatus having a die comprisinga slot for holding thermoplastic material, wherein the bottom of theslot is concave and substantially semi-cylindrical. A tool in theapparatus is adapted to enter the slot and is concave and generallycomplimentary to the slot bottom. The apparatus has means for urging atool into the die slot, and means for vibrating the tool at highfrequency. The heat generated by the vibrations causes a thermoplasticmaterial contained in the slot to melt.

Long et al. in GB 1,154,429 teach a process and apparatus for joiningthe ends of two textile threadlines. The apparatus comprises anultrasonic apparatus is mounted on a casing 4 which surrounds atransducer stack. A straight groove 5 is cut across the face of acoupling stub 3 to locate and support threadlines being joined. Aplunger 11 is mounted on a cam 7 for movement in and out of the stubgroove 5. The cam 7 rotates on a pivot 17 at one end of an arm 9 whichpivots on an axis on a support member 10. The plunger is slidablymounted in an arm 12 and bears against the surface of the cam throughthe action of a compression spring 13. The compression spring is opposedby a tensioning spring 14 attached to pivot 17. The pressure exerted bythe plunger is determined by the tensioning of the springs.

Other objects of the invention will be apparent from the followingdescription and claims.

DISCLOSURE OF INVENTION

A method for continuous operation of a fabric-weaving unit for weaving afabric made from thermoplastic cords or monoflaments comprises the stepsof (a) feeding a leading end of a first thermoplastic cord ormonofilament (30 a) into a weaving appartus through various reeds, dropwire slots, rolls and guides of the weaving apparatus and weaving thecord or monofilament (30 a) into a fabric, (b) continuing processing ofthe cord or monofilament (30 a) to a trailing end of the cord ormonofilament (30 a), (c) welding the trailing end of the cord ormonofilament (30 a) to a leading end of a second thermoplastic cord ormonofilament (30), and (d) continuing the operation of the weaving unitby weaving the second thermoplastic cord or monofilament (30) into afabric.

The method is illustrated using 2,000 to 20,000 dTex thermoplasticmonofilaments as fabric material.

In a preferred embodiment, the method is used with cords ormonofilaments comprising nylon.

The method is illustrated making a roll of fabric using 8 to 40 ends perinch (epi) cords or monofilaments in the warp direction and 1 to 8 epipick cords in the weft direction, using an ultrasonic welder.

The method is carried out so that the monofilaments or cords (30,30 a)are oriented such that at least one end thereof is fused in a weld (60),and preferably the weld (60) is oriented such that the lead end of theweld is fused so that a loose end (58) does not snag on any parts of theprocessing equipment.

Also provided is an apparatus for splicing thermoplastic cords ormonofilaments comprising a welder (16) mounted on a fixture (14), saidfixture (14) being rotatably mounted to a pole (12), said pole (12)being attached to a stand (15). The stand (15) is lightweight and caneasily be moved, and may be otherwise adapted to be mobile, or in analternative embodiment, may be fixed in position. In the illustratedembodiment, pole (12) is mounted vertically and the fixture (14) isadapted to rotate around the pole (12).

In the illustrated embodiment, the welder (16) is an ultrasonic welder.The welder (16) has a welding horn (18) which is used in conjunctionwith an anvil (20) for welding material. The anvil (20) may comprise aright feed cord alignment block (20 a) or a left feed cord alignmentblock (20 b).

Also provided is a mold for welding cord or filament ends comprising atop plate (32,48) and a lower plate (40,52), the top plate (32,48) beingadapted to be pressed together the lower plate (40,52), wherein the topplate (32,48) has a groove (34,50) which transverses more than ½ thelength of the top plate (32,48), and the lowerplate (40,52) has a groove(46,54) which traverses less than ½ the length of the lower plate(40,52) and an opening (44) at the termination of the groove (46,54).When the top plate (32,48) is aligned with and pressed together with thelower plate (40,52) to form a block (20) the groove (34,50) in the topplate (32,48) is in an opposite end of block (20) from the groove(46,54) in the lower plate (40,52), and the lower plate groove (34,50)overlaps with top plate groove (46,54) in the middle of block (20). Anopening (44) in lower plate (40,52) is adapted to receive a welding horn(18).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a front view of an apparatus of the invention.

FIG. 1a illustrates a side view of an apparatus of the invention.

FIG. 2 illustrates a view of an apparatus of the invention in proximityto the creel of a loom.

FIG. 2a illustrates a side view of an apparatus of the invention inproximity to the creel of a loom.

FIG. 3a illustrates a top plate of a cord alignment block (right feed).

FIG. 3b illustrates a side view of the plate of FIG. 3a.

FIG. 3c illustrates a bottom plate of a cord alignment block (rightfeed).

FIG. 4a illustrates a top plate of a cord alignment block (left feed).

FIG. 4b illustrates a bottom plate of a cord alignment block (leftfeed).

FIGS. 5 and 5a illustrate a knurled welding head used in the method ofthe invention.

FIG. 6 is a perspective view of a welding head in proximity to analignment block.

FIG. 7 illustrates a perspective view of an alignment block and anultrasonic welder mounted on a pole.

FIG. 8 illustrates a weld made according to the method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Traditionally, nylon and polyester twisted cords are tied to splice innew spools or to make a repair when the cord breaks.

Tied knots were used in an attempt to fasten one end of a nylonmonofilament (10,000 dtex) to another. However, such knots tend to bevery bulky and difficult to pass through the small openings of theweaving loom reeds and drop wires, and tend to slip apart when a tensionis applied. A nylon monofilament is a smooth, slippery and solid cord.It is relatively inextensible, since there is little or no twist in themonofilament.

An automatic mill knot device (air entanglement) could not be used dueto the absence of numerous fine filaments which make possible theentanglement. A trial using an epoxy adhesive did not provide sufficientbond strength and flexibility to be pulled through the weaving loom.

Another type of splice is made by tightly wrapping a fine yarn aroundoverlapped ends of the cord or monofilament. However, wrapping themonofilament increased the overall diameter at the splice, making itdifficult to pull the splice through the reeds and drop wires, and someof the splices would pull apart due to the slippery surface of themonofilament. Also, the cord ends would sometimes catch and snag on thereeds or drop wires.

Wrap splicing the individual monofilament ends at the creel was timeconsuming and labor intensive. Even if a wrap splice would have beensufficient to tie in a new creel, a wrap splice is unacceptable to makea repair if a monofilament breaks and has to be tied together tocontinue weaving. Also a monofilament wrap splice pulls loose as thewoven monofilament is processed in fabric treatment equipment.

Nylon is a thermoplastic material, and is representative of allthermoplastic materials that can be used in the invention.

Thermoplastic materials, while solid at moderate temperatures, soften ormelt and flow at higher temperatures without permanently altering theirchemical composition, and accordingly return to their original statewhen they return to a moderate temperature. Because of this property,thermoplastic materials can easily be joined at temperatures above themelting point of the materials by low temperature welding, especiallyultrasonic welding.

The present invention can be used with any type of welding equipmentsuitable for the materials being joined, such as heated presses, but isdescribed herein specifically using an ultrasonic welder for joiningthermoplastic materials.

With reference now to FIGS. 1 and 1a, in the illustrated embodiment ofapparatus that may be used in the method of the invention, the apparatus10 comprises a pole 12 attached to a stand 15, and a welding unit 16 isattached to pole 12 through mounting fixture 14. A power source 22,which may include an electronic interface, may be carried in stand 15.

The apparatus is lightweight and may be easily moved from position toposition as needed, so apparatus 10 can be moved to a welding job at aparticular loom. In the illustrated embodiment, stand 15 is fixed at theloom on which it is used.

Mounting fixture 14 may be slid up and down pole 12 for welding atdifferent heights, and may be rotated 360° on pole 12 for welding atdifferent angular positions relative to stand 15. Wheel 24 is attachedto a counterweight system which helps control movement of welder 16 asmounting fixture 14 is slid up and down pole 12.

In the illustrated embodiment, welder 16 is an ultrasonic welder havinga welding horn 18, and a cord alignment block 20 which is used as ananvil for welding.

By experimenting with a large number of different types of weldinghorns, it was discovered that for the purposes illustrated herein, aknurled welding horn 18 (FIG. 5) produced the best results. Thoseskilled in the art will recognize that other welding horns may givebetter results when used under different conditions.

With reference now to FIGS. 2 and 2a, apparatus 10 may be moved next tocreel 26 when a spool 27 of monofilament 30 is about to be depleted andit is time to attached a new spool 27 a of monofilament 30 a to the endof monofilament 30 before it passes through the loom (not shown). Theoperator will catch end 31 of cord or filament 30 and direct it towelding apparatus 10, and at the same time pull end 31 a of cord orfilament 30 a to apparatus 10 to weld them together. The new spool 27 ais then placed on the creel to replace old spool 27.

Those skilled in the art will recognize that the creel and or loom maybe equipped with sensors to indicate when the end of a filament or cord30 is detected.

Also, it is possible to replace one creel with another, so that all theconnections will be made when a new creel is moved into position at theloom.

Since a loom is relatively wide, apparatus 10 can be moved dependent onthe location of a spool 27 on the creel and its relationship to theloom. Also, to save space on the creel, spools 27 are stacked, andmounting fixture 14 can be raised or lowered on pole 12 to place welder16 in proximity to the height of a spool 27. Mounting fixture 14, asnoted above, can also be rotated on pole 12 if needed.

With reference now to FIGS. 3 and 4, a cord alignment block 20comprises, in the illustrated embodiment, a lower plate 32,48 and a topplate 40,52.

The cord alignment block 20 a illustrated in FIGS. 3a, 3 b and 3 c is aright feed block.

When apparatus 10 is placed by creel 26, and the mounting fixture 14 ispivoted on pole 12, monofilaments to be welded may pass on the right orthe left side of pole 12. Because monofilaments 30 and 30 a areoverlapping when a weld is made, and it is difficult make the overlapequal to the width of the weld, there may be a loose end of monofilamentat the weld. See FIG. 8. Since a loose end will likely snag in the loomtrain at a number of locations, it is important that a loose end be thetrailing end of the weld as the monofilament passes through the loom, sothat such snagging can be prevented. By providing a right feed cordalignment block 20 a (FIGS. 3a, 3 b, 3 c) and a left feed alignmentblock 20 b (FIGS. 4a, 4 b), the overlapping of the welded monofilamentends can be controlled so that any loose filament ends trail the weld asthe monofilament passes through the loom. When welder 16 is on the leftside of pole 12, left feed alignment block 20 b is used to make surefree end 58 of monofilament 30 trails weld 60 through the loom. Andlikewise, when the welder 16 is on the right side of pole 12, right feedalignment block 20 a is used to make sure the end of monofilament 30 isfused with weld 60 and the free end 58 is oriented so that it does notsnag the equipment.

To help make certain that at least one of the two welded ends ofmonofilament are integral with the weld, using the right feedmonofilament alignment block 20 a of FIG. 3 as an example, lower plate32 has a slot 34 for holding a monofilament 30 in the lower plate of themonofilament alignment block 20. Similarly, top plate 40 has a slot 46for holding a monofilament 30 a in top plate 40. When top plate 40 andlower plate 32 are pressed together and aligned, using alignment posts43 and alignment slots 38, monofilaments 30,30 a can be pushed intoalignment block 20 a through slots 34 and 46 so that they overlap in theopening 44 of alignment block 20 a. Opening 44 is adapted to receive awelding horn 18 when the welding operation is carried out. The end ofthe monofilament in slot 46 will be above the end of the monofilament inslot 34 in opening 44 when a weld is made. Since, as illustrated, slot34 is long enough to extend through opening 44, but the filament in slot46 is stopped within opening 44 by top plate 40 at edge 40 a, theoperator can visually make sure that the end of the monofilament in slot46 is under weld horn 18 when a weld is made.

Holes 36 are used to mount block 20 into the ultrasonic welding base.

With reference to FIG. 4, a similar but oppositely oriented (as comparedto FIG. 3) slot 50 is in lower plate 48, and an oppositely oriented slot54 is in top plate 52 in a left feed monofilament alignment block 20 b.Except for the orientation, left feed alignment block 20 b is used inthe same manner as described for alignment block 20 a.

In the illustrated embodiment, the monofilament alignment blocks 20 a,20 b have hinges 38 for convenience of handling. Those skilled in theart will recognize that the lower plates 32, 48 will have to beseparated from top plates 40, 52 after a weld has been made, to removewelded monofilaments 30, 30 a from the monofilament alignment block 20.

FIGS. 6 and 7 illustrate two different enlargements of portions of theapparatus of the invention.

With reference to the figures, in the method of the invention, a stand15 is placed in the proximity of a loom near the creel stand 26. On theright side of creel stand 26, a right feed alignment block 20 a is usedwith apparatus 10 as monofilament 30 a is welded to the end of adepleted roll of monofilament 30 in creel 26. Filament 30 is pushed intoslot 34 in top plate 32 and filament 30 a is pushed into slot 46 inlower plate 40 and weld horn 18 is moved into opening 44 in lower plate40. A weld 60 is made making sure that the end of filament 30 a isincorporated in the weld. If a free end 58 of filament 30 escapes theweld 60, this will not hinder the processing of filament 30 a throughthe loom because filament 30 a passes through the loom in the directionof arrow ‘a’, and end 58 trails weld 60 through the loom and cannotcatch or snag on the various parts of the loom.

In a similar manner, when stand 15 is placed on the left side of creel26 a, left feed monofilament alignment plate 20 b will be used toprevent a free end 58 from snagging in the loom.

These splices can be pulled through the weaving loom at requiredtensions, and easily pass through the reeds and drop wire slots on theweaving loom without failing.

Although the invention was originally developed to address the problemsencountered in weaving monofilament fabric, those skilled in the artwill recognize that the invention can be used with cords made ofthermoplastic materials.

The invention is further illustrated with reference to the followingexample.

EXAMPLE

Feasibility studies were conducted using hand operated prototypeequipment for ultrasonic splicing of individual cord ends. For theseearly development trials at the fabric mill, the ultrasonic welder wasrented from Branson Ultrasonic Incorporation. The 150 watt unit, ModelE150, Power Supply TW-1 Converter used a ½-inch diameter knurl tip hornwith the alignment fixture.

Dukane Corporation manufactured two ultrasonic welding units to Goodyearspecifications that were used to connect nylon monofilaments to eachother. The welding units are Dukane 410 7OOAT 40 kHz thrusters with ahorn that has a ½ inch diameter knurled tip. Each assembly consists of astand, pole, and the ultrasonic press on a platform which can movevertically and rotate around the pole. Each unit is installed at the endof a creel row in the center of the two-sided creel, and just before thefirst set of drop wires. Welding in a new creel will consists ofstarting at the bottom of one side of a row and working up to the top,rotating the welding press fixture 180 degrees at the top, lowering thefixture to the bottom, and continuing welding of the other side startingfrom the bottom and progressing toward the top. The fixture is stored atthe top of the pole until a new creel is needed.

Welding conditions for the monofilament are: weld time 1.5 sec, holdtime 1.0 sec, and weld pressure of 30 psi, and holds pressure of 40 psi.Typical weld strength observed was 25-30 pounds force.

Two mold fixtures are used to position the monofilaments prior to theactual welding with the ½-inch diameter horn. One fixture is for theleft side of the creel stand and the other is for the right side of thecreel stand. Alignment of the nylon monofilaments is important such thatthere are no leading weld tabs, e.g. monofilament ends that might catchor snag on sharp edges as the welds are pulled through the weaving unit.This is accomplished by pulling the bottom monofilament back ¼ inch (inthe mold fixture) just before welding. The alignment mold is split atthe plane of the monofilament such that after the two ends are attached,the mold is opened and the filament can be released.

By experimentation it was determined that the following weld parametersand specifications give good results under the conditions describedherein.

TABLE I Dukan 410 700AT 40 kHz, Recommended Settings for IndividualMonofilament Splices, 10,000 dtex Round Nylon Monofilament Power SupplyUnit Weld Time, sec 1.5 Hold Time, sec 1.0 Power Setting 15 SwitchSetting Operate L1 Function 0 (disabled) Welding Press Stand P1-WeldPressure, psi 30 P2-Hold Pressure, psi 40 Down Speed Control 3 turns CCPre-Trigger Adj 10 (bottom) End Weld Adj 10 (bottom) Mechanical Stop 15mils above mold Trigger control 0.1 turns > Minimum setting

Table II illustrates weld strength for a sample weld.

TABLE II Ultrasonic Welded Splices Welding Conditions Established AboveWelder Left Right Tensile St, N 28.2 30.2 Std Div, N  3.0  2.9 FailureType * * * Mixture of weld failures (bond failure at interface) weldbreaks (top monofilament breaks at interface)

Table III illustrates the steps used to form a weld.

TABLE III PROCEDURE FOR WELDING ONE MONOFILAMENT TO ANOTHER 1. Fixsetting on the unit for output at 1.5 weld time at 1.5 seconds, holdtime at 1.0 second, and switch setting to OPERATE. 2. Use properAlignment mold tbat matches the side of Creel working on: L - left sideof creel row, R - right side of creel row. 3. Turn on air pressure tothe welding press, setting for weld psi at 30 and hold psi at 40. 4.Place monofilament in side 1 (CREEL) on the filament alignment block andinsert to the stop point. 5. Place monofilament in side 2 (LOOM) on thefilament aligmnent block and insert to the stop point. 6. Pull back onthe monofilament on side 1 about ¼ inch so that the end of themonofilament is aligned with a mark on the filament alignment block. 7.Weld the monofilament together by pushing down on the two start buttonssimultaneously. The rest of the cycle is completed automatically. 8.Weld the creel row from the bottom to the top. Rotate the welder at thetop 180 degeees to start the other side of the row. Lower the unit andstart from the bottom.

What is claimed is:
 1. A method for continuous operation of afabric-weaving unit for weaving a fabric made from thermoplasticmonofilaments comprising the steps of (a) feeding a leading end of afirst thermoplastic monofilament (30 a) into a weaving apparatus throughvarious reeds, drop wire slots, rolls and guides of said weavingapparatus and weaving said monofilament (30 a) into a fabric, (b)continuing processing of said monofilament (30 a) to a trailing end ofsaid cord or monofilament (30 a), characterized by (c) ultrasonicallywelding said trailing end of said monofilament (30 a) to a leading endof a second thermoplastic monofilament (30) (d) orienting monofilamentsor cords (30,30 a) such that at least one end thereof is fused in a weld(60), and (e) orienting a weld (60) on said monofilaments or cords(30,30 a) such that a weld (60) leads any loose ends (58) throughprocessing equipment, (f) continuing the operation of said weaving unitby weaving said second thermoplastic cord or monofilament (30) into afabric.
 2. An apparatus for splicing thermoplastic cords ormonofilaments comprising an ultrasonic welder (16) mounted on a fixture(14), said fixture (14) being rotatably mounted to a pole (12), saidpole (12) being attached to a stand (15) wherein said stand (15) isadapted to be mobile around a creel row (26).
 3. The apparatus of claim2 wherein the welder (16) has a welding horn (18) which is used inconjunction with an anvil (20) for welding material wherein the anvil(20) may comprise a right feed cord alignment block (20 a) or a leftfeed cord alignment block (20 b).